Whitespace-only changes on a line would result in a replace chunk that

could trigger move detection. This happened because we strip lines

before calculating moved lines, and didn't check that the same line was

modified, resulting in the line matching itself.
We now compare the offsets into the chunk to make sure that matched

lines aren't in the same location within the chunk. By this point, we

already know the content is matched after being stripped, so an offset

change should be sufficient to prevent this problem from occurring.

Tested with a diff that exhibited the behavior. It went away after this.
Existing diffs with valid move flags for replace lines continued to work.
All existing unit tests passed.
A new unit test was added to test leading and trailing whitespace changes,

adding and removing.